In recent years, environmental pollution caused by organic chemicals has become a concern in many parts of the world. In particular, many aromatic compounds possess biotoxicity, carcinogenicity, mutagenicity, endocrine disrupting activity, etc., and therefore their influence on human beings and ecosystems causes concern.
In order to prevent environmental pollution caused by organic chemicals, various laws and regulations have been enforced, but no satisfactory effect has yet been achieved. One of the probable causes of such pollution is the discharge of industrial and domestic drainage, leachate from landfills, etc., without having been satisfactorily purified. To prevent such environmental pollution, it is necessary to satisfactorily purify polluted drainage, etc., before discharging it into the surroundings.
Examples of organic chemicals that may cause environmental pollution include alkylphenols, bisphenol A, dioxin, PCBs, etc. They are difficult to decompose, exhibit endocrine disrupting activity, and adversely affect human beings and ecosystems even at low concentrations.
Examples of methods for decomposing and/or removing such organic chemicals (also referred to herein as contaminants) include biological methods utilizing microorganisms (for example, Non-patent Document 1), physical methods utilizing activated carbon and like adsorbents (for example, Non-patent Document 2), chemical methods wherein organic chemicals are decomposed by being irradiated with ultraviolet light (for example, Non-patent Document 3), etc. However, using biological methods, it is difficult to decompose a variety of contaminants with a single microorganism, and therefore a microorganism suitable for each contaminant has to be found. Moreover, even if suitable microorganisms are obtained, it is necessary to create the conditions in which the microorganisms can exhibit sufficient decomposition ability in actual practice. Furthermore, since a microorganism can decompose a contaminant only slowly, there is a problem in that the decomposition and removal of the contaminant takes time. In contrast, using physical methods, although various contaminants can be adsorbed, a separate step for treating the collected contaminants becomes necessary. Using chemical methods, organic chemicals are decomposed only at a slow rate when using a mild method and some organic chemicals cannot be decomposed at all depending on the type thereof, and therefore the use of toxic chemicals (oxidants, strong acids, etc.) is necessary to accelerate the decomposition of such organic chemicals.
In view of such circumstances, a method for decomposing and/or removing contaminants in which various contaminants can be safely and readily treated in a short time is being sought.
[Non-patent Document 1] World Journal of Microbiology & Biotechnology, 20, 517-522 (2004)
[Non-patent Document 2] Chemosphere, 58, 1535-1545 (2005)
[Non-patent Document 3] Journal of Hazardous Materials, B101, 301-314 (2003).